LIGNANS AND NEOLIGNANS FROM STEMS OF PIPER WIGHTII

Studies of the petroleum ether extract of the stems of Piper wightii M iq. resulted in the isolation of three novel 2'-oxo-8.1'-and 4'-oxo-8. 5'-neolignan with unusual structures, namely -methylenedioxy-2'-oxo-De lta(3',5',8')-8.1'-lignan -dimethoxy-6-(2-propenyl)-2,4-cyclohexadien- 1-one) (1), 4-methylenedioxy-2'oxo-Delta(3',5',8')-8.1'-lignan -dimeth oxy-6-(2-propenyl)-2,4-cyclohexadien-1-one) (2) and -methylenedioxy-4' -oxo-Delta(2',5',8')-8.5'-lignan -dimethoxy-4-(2-propenyl)-2,5-cyclohe xadien-1-one) (3) together with one novel tetrahydrofuran lignan, ,4'- dimethoxy-3,4-methylenedioxy-8.8',7.O.7-lignan 3,4-dimethyl-2-tetrahyd rofuranyl]-1,3-benzodioxol) (4). The structures were elucidated on the basis of spectroscopic data (H-1-,2D- and C-13 NMR,NOE,UV,IR and MS). Additionally, two known neolignans, hylenedioxy-6'-oxo-Delta(4',8')-8 .3',7.O.2'-lignan (fargesone A, 5) and thylenedioxy-6'-oxo-Delta(4',8' )-8.3',7.O.2'-ligan (fargesone B,6) were isolated for the first time f rom p. wightii.